This invention relates to stand mixers, by which is meant the kind of motor-driven kitchen machine which is used to mix, or otherwise process, ingredients in a bowl by powered movement of one or more shanked tools which depend into the bowl from a head unit that carries a downwardly-facing drive outlet, powered by the motor, to which the shank, or shanks, of the tool, or tools can be fitted for use.
Such mixers conventionally comprise a generally C-shaped casing which provides a pedestal-like support for a mixing bowl, and a generally upright support portion supports the head unit so that it extends overhead of the bowl. Moreover, the powered movement of the shanked tool or tools is often, though not necessarily, planetary in nature.
Stand mixers such as the Kenwood Chef kitchen machine are well known and have been well established in use for many years. Over the years, mixers of this kind have been adapted and developed so as to perform an ever broadening range of functions, and many such appliances provide, for example, a plurality of additional drive outlets running at different speeds and with differing torque characteristics, thus enabling them to drive a number of attachments, such as blenders and mincers, which, between them, can perform a wide range of tasks. This is beneficial for the user, because a single machine can be used to selectively host several attachments and thus perform a range of tasks which would otherwise require the purchase and storage of several bespoke kitchen machines, each with their own motors and associated equipment.
Typically, the additional drive outlets are located at different places on the stand mixer body, depending to an extent on the configuration and purpose of the attachments they are to drive. In particular, it is usual for a high-speed outlet, capable of powering a blender attachment, for example, to be provided on the upper surface of the head unit and close to its junction with the upright portion of the stand mixer's casing.
If the stand mixer is also intended to drive a food processor attachment, however, it is necessary either to provide a separate outlet elsewhere on the stand mixer or to provide a separate, external gearbox that can be coupled to the blender drive outlet to reduce the driving speed and also convert the drive outlet configuration to one that can couple to a conventional food processor bowl. Neither option is particularly desirable, since the provision of separate drive outlets for blender and food processor attachments is awkward and costly, requiring additional gears and pick-offs from the main drive train, and the storage and fitment of separate gearboxes is a nuisance for the consumer.
It is also necessary to provide an economical and robust coupling between the motor and its primary drive train, the additional outlets and the slow-speed planetary or other drive outlet used to power the aforementioned shanked tool or tools, such as dough hooks and the like, which are provided for mixing ingredients placed in the bowl that stands on the pedestal beneath the head unit.
It is an object of the invention to address some at least of the above considerations and, in accordance with one aspect of the invention there is provided a stand mixer comprising a head unit having a lower surface presenting, in operation, a downwardly-facing drive outlet for driving in rotation at least one tool suspended therefrom, support means for supporting said head unit with said downwardly-facing drive outlet above a receiving location for a mixing bowl, and driving means including an electric motor and associated transmission means for conveying rotary drive to said drive outlet, the mixer being characterised by the provision of first and second coaxial driving outlets presented on an upper surface of said head unit; said coaxial outlets running at different speeds and being driven from said motor by means of an epicyclic gearbox; the motor being housed in said support means with its drive shaft in substantial alignment with said coaxial drive outlets. By this means, attachments requiring different driving characteristics can be driven from the inner or outer of the coaxial outlets as appropriate in a stable and convenient manner.
The provision of (preferably, at least) two coaxial drive outlets operable at distinct speeds improves the range of attachments (for example, to include high and low speed attachments) that may be driven by the stand mixer. Furthermore, the downwardly-facing drive outlet that is, preferably, offset from the coaxial drive outlets may be used simultaneously alongside one (or both) of the coaxial drive outlets. Advantageously, the downwardly-facing drive outlet and coaxial drive outlets are driven by the same motor and epicyclic gearbox arrangement, thereby eliminating the need for each drive outlet to have a separate motor and corresponding gearing.
Preferably, the inner of said coaxial drive outlets and the sun wheel of said epicyclic gearbox are driven directly, and at a relatively high speed (i.e. the operating speed of the motor), by said drive shaft, and the outer of said coaxial drive outlets is driven, at a lower speed then the inner drive outlet, from a planet carrier of said gearbox.
In a preferred arrangement of the above kind, said transmission means includes transfer means configured to convey, from said epicyclic gearbox to said downwardly-facing drive outlet, rotational drive at a substantially lower speed than said outer drive outlet. Advantageously, the downwardly-facing drive outlet is operable by means of the motor and the epicyclic gearbox.
It is particularly preferred that said transfer means comprises a belt and pulley system, and that the driven pulley of said belt and pulley system is driven from the planet carrier of said epicyclic gearbox.
Conveniently, in such a system, the driven pulley and a driving member for the outer of said coaxial outlets are integrally formed and are securely but removably attached to said planet carrier.
Preferably, in such circumstances, said planet carrier is of metallic construction and formed with a central aperture to accommodate the drive shaft of said motor; a lip region of the planet carrier surrounding the aperture supporting an axially-extending central plastic drive form, overmoulded thereon, which presents external surface features complementary to internal surface features formed centrally of the said integral driving member and driven pulley, whereby the said integral driving member and driven pulley can be press-fitted to said drive form.
Further preferably, the external surface of the drive form is provided with one component of an annular clip, the other component of which is provided on the internal surface of said integral driving member and driven pulley whereby, when press-fitted together, the two components of the clip snap into place, thereby latching the driving member and driven pulley securely to the drive form, but facilitating their separation, by unclipping them, if required for servicing.